Sex reversal using 17 α-methyltestosterone immersion and its effect on sex reversal and growth performance of Nile tilapia (Oreochromis niloticus L., 1758)

Abstract

The study aimed to evaluate the optimal dose of 17 α-methyltestosterone (MT) and stocking density using immersion method for maximum survival, masculinization rates and growth performance of Nile tilapia (Oreochromis niloticus). The experimental design employed complete randomization including three concentrations of 17 α-methyltestosterone (1.5, 2.0, and 2.5 mg/L) and three stocking densities of 500, 750, and 1000 fish/L and a control group, arranged in three replicates. The control groups consisted of 3 stocking densities of 500, 750, & 1000 fish/L and fish were kept in glass aquaria containing MT-free water. Fish were exposed to MT solution for 2 h, and the fish were then transferred to nursery in hapas in earthen ponds at a density of 1,000 fish/m2 for 60 days. After the hormone treatment and 60 days of rearing, the highest survival rate was found in the control group. The male ratios in the MT treatments ranged from 78.9 to 91.1% and were statistically higher than that in the control (55.1%) (P < 0.05). The most effective doses and stocking density in sex-reversal of the tilapia fry using immersion method were 2.0 mg 17 α-MT/L and 750 fish/L, respectively. The mean weight and length of fish in the MT treatments were greater than those in the control treatment, although the difference was not statistically significant (P > 0.05). The results also showed that the average weight of experimental fish was directly proportional to the hormone concentration but inversely proportional to the stocking density. Based on the study findings, the recommended dose for producing maximum mono-sex male tilapia is 2.0 mg 17 α-MT /L, and the most suitable stocking density is 750 fish/L.